In telecommunication systems, links are established between nodes of a system for conveying information. Efficient use of these links requires enforcement of communication parameters defining when nodes at each end of a link anticipate information from the other unit. These parameters, in efficient bandwidth systems, comply with extremely tight tolerances to maximize information exchange. These parameters may include propagation delays between nodes of a network and transmit frequencies combined with path-introduced frequency errors, such as Doppler frequency shifts. As the communication parameters become more predictable and precise, guardbands on communication channels, such as frequencies and timeslots, can be reduced to accommodate exchange of additional information.
In conventional static or lightly dynamic telecommunication networks, these communication parameters may be refined upon the establishment of a communication link and relied upon throughout a communication session. However, in a dynamic communication system where these communication parameters are rapidly changing, communicating nodes such as subscriber units continually refine and update these communication parameters in order to maintain the prescribed tolerances of the system.
Conventional systems evaluate each transmission employing dynamic communication parameters to determine the precision of the employed parameters. When the parameters exceed threshold values, as defined by system specifications such as channelized communication frequencies or timeslots, the receiving system informs the transmitting node of correction values which bring the communication parameters into compliance with system requirements.
This approach is suitable when established communication links are not susceptible to transient effects, such as temporary fades due to obstructions or fleeting interference. However, in dynamic communication systems where communication parameters are short-lived, even brief fades of communication links cause communication parameters to become stale and ineffective when utilized following communication link fades. A receiving system will not recognize a node such as a subscriber unit, that employs out-dated communication parameters, due to the precise tolerances of channelized communication systems. When a subscriber unit is not recognized, the communication link will be terminated. Since most fades are of relatively short duration, the decision to drop the communication channel every time a fade occurs is undesirable. On the other hand, a subscriber unit should not be allowed to operate out of synchronization with its assigned channel because the resulting signal could interfere with one or more other channels.
Consequently, a process to predict dynamic communication parameters continuously throughout brief fades becomes desirable. This process would ensure that a subscriber unit will have revised its communication parameters to comply with the current system dynamics when the fade terminates. Following these brief fades, the system can be resynchronized. During this resynchronization process, the communication link could experience additional fades. Unfortunately, if resynchronization is not complete prior to additional fades, a channel may be dropped even though communication is otherwise able to proceed.
Accordingly, in addition to predicting dynamic communication parameters continuously throughout intermittent changes, there is a significant need for a method that improves the resynchronization process based on outage characteristics, so that a channel will not be erroneously dropped.